14041 Background: MORAb-009 is a monoclonal antibody that targets mesothelin, a cell surface adhesive protein overexpressed in pancreatic, ovarian, non-small cell lung carcinomas and mesothelioma and has minimal expression in normal tissue. The target is over-expressed by tumor cells. It was identified as one of the most prominent, differentially expressed cell surface antigens on pancreatic adenocarcinoma using SAGE of primary tumors vs. normal pancreatic tissue. In vitro studies show MORAb-009 to be effective in mediating cell killing by ADCC and inhibiting cell adhesion.. In xenograft models, MORAb-009 has single agent anti-tumor activity enhanced by the addition of chemotherapy. Toxicology studies show no toxicity in non-human primates and no significant binding to non-tumor tissues. Methods: Sequential cohorts of 3 patients received MORAb-009 intravenously on days 1, 8, 15 and 22 at doses of 12.5, 25, 50 and 100 mg/m2. Major inclusion criteria are the presence of a mesothelin-positive tumor with progression on primary therapy, acceptable organ function, ECOG PS 0–2, and measurable disease by CT. Safety pharmacology studies include chemistry, hematology, urinalysis and EKG. Tumors were re-imaged at day 35. Results: 11 patients have received MORAb-009 at doses up to 100 mg/m2. 6 patients had mesothelioma, 3 had pancreatic cancer and 2 had mesothelin-positive ovarian cancer. 4 patients exhibited grade 1 (3) or 2 (1) infusion reactions; no dose limiting toxicity was observed. A subject in the 50 mg/m2 cohort with pancreatic cancer who progressed on gemcitabine showed stable disease by CT and a drop in CA 19/9. Based on the response, this patient continues on extended MORAb-009 therapy. Enrollment to the final cohort of 200mgs/m2 is ongoing, as are pharmacokinetic and anti-MORAb-009 antibody analysis. Conclusion: MORAb-009, a monoclonal antibody against mesothelin is safe and well tolerated at doses up to 100 mg/m2. One subject with previously progressive pancreatic cancer had disease stabilization. In light of the positive preclinical data and safe clinical profile, this study supports further evaluation of the efficacy of MORAb-009 in mesothelin-positive tumors. No significant financial relationships to disclose.